Vehicle communication system using incompatible modulation techniques

ABSTRACT

A locomotive communication system includes a lead communication device wirelessly communicating command messages to remote communication devices onboard a rail vehicle system during a messaging cycle. The lead device receives reply messages from the remote devices during the messaging cycle in response to the command messages. The lead device receives a status signal from at least one of the remote devices during a guard interval that follows completion of the messaging cycle. The lead device communicates the command message and receives the reply messages using analog modulation or digital modulation. The lead communication device also receives the status signal using the other of the analog modulation or the digital modulation. The command messages, the reply messages, and the status signal are communicated using a designated frequency channel.

FIELD

The subject matter described herein relates to locomotive communicationsystems.

BACKGROUND

Vehicle systems can have multiple propulsion-generating vehicles thatinclude communication devices for the vehicles to communicate with eachother. The vehicles can communicate with each other to coordinateindividual vehicle movements so that the entire vehicle system movesalong routes. For example, locomotives can communicate with each otherusing wireless communications so that one locomotive can remotely directthe throttle settings, brake settings, etc., of the other locomotives inthe same rail vehicle system.

The locomotives may send messages (also referred to as signals)back-and-forth to ensure that messages commanding changes in throttlesettings and/or brake settings are sent and that messages indicating thechanges were received are sent. These vehicle systems typically employ acontention scheme to prevent overlapping interference between thedifferent messages. For example, some locomotives use a slotted alohaprotocol to allow multiple trains containing multiple locomotives to usethe same frequency channel for communicating messages between thelocomotives in the same train. This protocol divides the times at whichdifferent locomotives can communicate over the channel into time slotsthat are accessed on a prioritized but randomized basis.

Once a lead locomotive from a one train seizes the channel, that leadlocomotive and the remote locomotives that are controlled by that leadlocomotive have exclusivity of the channel for a defined period of time.This channel exclusivity allows for data communication between the leadlocomotive and the remote locomotives to occur without interference fromcommunication between other locomotives using the same channel.

This scheme relies on all locomotives within radio range to receive aradio protocol preamble from other transmitters on the channel to forcethe locomotives to hold off channel access for a preset period of time.In the current implementation, this occurs using Frequency Shift Keying(FSK) modulation. Other modulation schemes cannot be used at the sametime on the same channel due to the incompatibility of the modulationschemes. For example, these locomotives or other devices cannot useShaped Offset Quadrature Phase Shift Keying (SOQPSK) on the same channeland at the same time as the two modulation methods are mutuallyincompatible and neither modulation method would hold off transmittingfor the other method.

BRIEF DESCRIPTION

In one embodiment, a locomotive communication system includes a leadcommunication device configured to wirelessly communicate a commandmessage to one or more remote communication devices onboard a railvehicle system during a messaging cycle. The lead communication deviceis configured to receive one or more reply messages from the one or moreremote communication devices during the messaging cycle in response tocommunicating the command message. The lead communication device also isconfigured to receive a status signal from at least one of the remotecommunication devices during a guard interval that follows completion ofthe messaging cycle. The lead communication device is configured tocommunicate the command message and receive the one or more replymessages using a first modulation comprising one of analog modulation ordigital modulation. The lead communication device also is configured toreceive the status signal using a different, second modulationcomprising the other of the analog modulation or the digital modulation.The lead communication device also is configured to communicate thecommand message and receive the one or more reply messages and thestatus signal using a designated frequency channel.

In one embodiment, a method includes wirelessly communicating a commandmessage from a lead communication device to one or more remotecommunication devices onboard a rail vehicle system during a messagingcycle, wirelessly receiving one or more reply messages from the one ormore remote communication devices during the messaging cycle in responseto communicating the command message, and wirelessly receiving a statussignal from at least one of the remote communication devices during aguard interval that follows completion of the messaging cycle. Thecommand message and the reply message are communicated using a firstmodulation comprising one of analog modulation or digital modulation.The status signal is received using a different, second modulationcomprising the other of the analog modulation or the digital modulation.The command message, the reply message, and the status signal arecommunicated using a designated frequency channel.

In one embodiment, a locomotive communication system includes a leadcommunication device configured to be disposed onboard a lead locomotiveof a rail vehicle system. The lead communication device is configured tocommunicate with one or more remote communication devices according to adefined messaging cycle to control movement of the rail vehicle system.The one or more remote communication devices are disposed onboard one ormore remote locomotives in the rail vehicle system. The messaging cycleincludes a first time slot for the lead communication device to send acommand signal to the one or more remote communication devices using afirst modulation scheme on a single frequency channel and one or moresubsequent second time slots for the one or more remote communicationdevices to send a reply signal to the lead communication device usingthe first modulation scheme on the single frequency channel. The leadcommunication device is configured to receive a status signal from atleast one of the remote communication devices using a second modulationscheme on the single frequency channel. The first modulation scheme andthe second modulation scheme are incompatible with each other.

In an embodiment, a system includes a lead communication deviceconfigured to be disposed onboard a vehicle system. The leadcommunication device is configured to wirelessly communicate a commandmessage to one or more remote communication devices onboard the vehiclesystem during a messaging cycle. The lead communication device isconfigured to wirelessly receive one or more reply messages from the oneor more remote communication devices during the messaging cycle inresponse to communicating the command message. The lead communicationdevice is configured to wirelessly receive a status signal from at leastone of the remote communication devices during a guard interval thatfollows completion of the messaging cycle. The command message and thereply message are communicated using a first modulation comprising oneof analog modulation or digital modulation. The status signal isreceived using a different, second modulation comprising the other ofthe analog modulation or the digital modulation. The command message,the reply message, and the status signal are communicated using adesignated frequency channel.

BRIEF DESCRIPTION OF THE DRAWINGS

The inventive subject matter may be understood from reading thefollowing description of non-limiting embodiments, with reference to theattached drawings, wherein below:

FIG. 1 illustrates one example of a communication system;

FIG. 2 illustrates one example of several vehicle systems withinwireless range of each other;

FIG. 3 illustrates one example of a timing diagram for a messaging cycleof one of the vehicle systems shown in FIG. 2;

FIG. 4 illustrates one example of a timing diagram having guardintervals;

FIG. 5 illustrates one example of one of the vehicles shown in FIG. 1;and

FIG. 6 illustrates a flowchart of one embodiment of a method forcommunicating within a vehicle system shown in FIG. 1.

DETAILED DESCRIPTION

One or more embodiments of the inventive subject matter described hereininclude communication systems that provide for the use of incompatiblemodulation schemes to be used to communicate on the same channel by thesame devices. The incompatible modulation schemes can be different typesof data modulation that cannot be used at the same time on the samefrequency due to the types of data modulation interfering with eachother. As one example, one modulation scheme can be an analog modulationscheme while another modulation scheme can be a digital modulationscheme. In one embodiment, one of the modulation schemes is FrequencyShift Key (FSK) modulation and the incompatible modulation scheme isShaped Offset Quadrature Phase Shift Keying (SOQPSK) modulation.Alternatively, other incompatible modulation schemes may be used. Forexample, minimum shift keying (MSK) modulation and SOQPSK modulationcould be used, binary phase shift key (BPSK) modulation and quadraturephase shift key (QPSK) modulation could be used, amplitude shift key(ASK) modulation and quadrature phase shift key (PSK) modulation couldbe used, continuous phase frequency shift key (CPFSK) modulation andQPSK modulation could be used, quadrature amplitude modulation (QAM) andGaussian minimum shift key (GMSK) modulation could be used, or the like.

Under other circumstances where the inventive subject matter describedherein is not used, the mixing of the incompatible modulation methodswithin the same channel and within the same geographical area would notbe possible due to inherent incompatibilities and the eventual messagecollisions that would occur. For example, the concurrent or simultaneouscommunication of messages formed using the incompatible modulationschemes using the same frequency and within close enough proximity toeach other (that the messages interfere with each other) may not becurrently possible. One or more embodiments of the inventive subjectmatter described herein utilize a guard interval that is present betweenvehicle message transmissions to provide non-conflicting transmissiontime and bandwidth using a legacy (e.g., existing) communication systemto exploit the benefits of one modulation scheme over the other (e.g.,the higher data speeds available with SOQPSK modulation). Additionalchannel bandwidth can be achieved without adding additionalchannelization or sacrificing performance of the legacy system.

Some communication systems use timing protocols to allow multiplecommunication devices to communicate with each other using the samechannel (e.g., the same frequency). For example, the current LOCOTROLsystem by which rail vehicles (e.g., locomotives) in the same railvehicle system (e.g., train or consist) communicate with each other usesa modified Slotted Aloha protocol to allow multiple different trainscontaining multiple locomotives to use the same channel. The vehiclethat commands other vehicles in the same vehicle system can be referredto as the lead vehicle or lead locomotive, while the vehicles that arecommanded by the lead vehicle can be referred to as the remote vehiclesor remote locomotives. The communication scheme divides the channel timeinto time slots that are accessed on a prioritized but randomized basis.Once a particular lead vehicle from a particular vehicle system (e.g.,train) seizes a channel for communication, that lead vehicle and theremote vehicles in the same vehicle system have exclusivity of thechannel for a finite period of time, thus allowing data communicationsbetween the lead vehicle and all remote vehicles to occur withoutinterference (e.g., from other lead vehicles or remote vehicles in othervehicle systems).

The communication scheme also relies on the vehicle communicationdevices that are within radio range of each other to receive a radiomessage protocol preamble (referred to herein as Barker 1 and Barker 2)from other communication devices that are sending messages on thechannel to force the receiving communication devices to hold off onaccessing the channel for a preset period of time. This can occur usingone type of modulation scheme (e.g., FSK modulation). But, this alsoprevents the simple addition of more communication devices to thevehicle system that operate with a different modulation scheme (e.g.,SOQPSK modulation) as the modulation schemes are mutually incompatibleand neither modulation method would hold off transmitting messages toallow the other modulation method to send messages. That is, a deviceusing FSK modulation would not receive and understand that aSOQPSK-modulated message indicates that another device is using thechannel at that time. Instead, the device using FSK modulation wouldcontinue communicating messages that interfere with and preventsuccessful communication of the SOQPSK-modulated messages.

In one embodiment of the inventive subject matter described herein, acommunication system uses a guard interval that is built into thecommunication scheme or schedule of one modulation technique. In atleast one contention scheme, after the last vehicle within a vehiclesystem has completed the last message transmission of the last vehicle,a minimum guard interval is required by the contention scheme of thecommunication system before any other vehicle may access the channel.For example, the last remote locomotive in a train to send a reply orstatus message to the lead locomotive in the train may be required bythe contention scheme to wait for a designated period of guard time(also referred to as a guard interval) before any other lead locomotivecan communicate on the same channel. During this guard interval, thecommunication systems and methods described herein can use anothermodulation scheme, such as the SOQPSK modulation scheme, forcommunication of additional messages, thereby permitting additional dataand/or control messages to be exchanged within a vehicle system.

While the description herein focuses on rail vehicles such aslocomotives and vehicle systems such as trains and rail consists, notall embodiments of the inventive subject matter are limited to railvehicles. For example, the inventive subject matter can be used inconnection with other vehicles (e.g., automobiles, mining vehicles,off-highway vehicles, marine vessels, etc.) and/or other communicationdevices (e.g., communication devices that are not onboard vehicles).With respect to vehicle systems, not all embodiments are restricted tovehicle systems formed from mechanically coupled vehicles. For example,some embodiments of the inventive subject matter can be used with railvehicles that are mechanically connected with each other by couplers ina train or rail vehicle consist. Other embodiments of the inventivesubject matter can be used with vehicles that are logically connectedbut not necessarily mechanically connected with each other. Vehicles canbe logically connected with each other in a vehicle system when thevehicles communicate with each other to coordinate movements of thevehicles with each other so that the vehicles travel together alongroutes as a vehicle system.

FIG. 1 illustrates one example of a communication system 100. Thecommunication system 100 includes communication devices 102 (e.g.,devices 102A-D) disposed onboard different vehicles 104 (e.g., vehicles104A-D) in a vehicle system 106 formed from the vehicles 104 andadditional vehicles 108. The vehicle system 106 can be a rail vehiclesystem with the vehicles 104 being locomotives and the vehicles 108being cargo cars, rail cars, passenger cars, or the like. Alternatively,the vehicle system 106 can be a non-rail vehicle system formed frompropulsion-generating vehicles 104 and non-propulsion-generatingvehicles 108. The vehicles 104, 108 may be mechanically coupled witheach other in the vehicle system 106 directly or indirectly (e.g., by atleast one additional vehicle 104, 108). The vehicles 104, 108 can bemechanically connected with each other by couplers 112. Alternatively,the vehicles 104 and/or 108 may not be mechanically coupled with eachother but may be logically coupled with each other without mechanicalcouplings. The vehicles 104, 108 can travel together in the vehiclesystem 106 along one or more routes 110.

The communication devices 102 represent hardware circuitry that includesand/or is connected with one or more processors (e.g., one or moremicroprocessors, one or more field programmable gate arrays, one or moreintegrated circuits, and/or the like) that perform the operationsdescribed herein in connection with the communication devices 102. Thecommunication devices 102 can include or represent transceivingcircuitry such as modems, routers, antennas 120, switches, and the like.The communication devices 102 can run one or more software applicationsthat direct the operations of the processors and/or transceivingcircuitry. The communication devices 102 send and/or receive datasignals or messages between the communication devices 102. One or moreother pieces of equipment onboard the vehicles 104 can communicate datawith each other via the communication devices 102, as described herein.

The communication devices 102 wirelessly communicate with each other tocoordinate operations of the vehicles 104 with each other. In oneembodiment, one of the communication devices 102A is a leadcommunication device onboard a lead vehicle 104A. The remainingcommunication devices 102B-D may be remote communication devices onboardcorresponding remote vehicles 104B-D. The lead vehicle 104A can remotelycontrol movements of the remote vehicles 104B-D by wirelessly sendingmessages to the remote communication devices 102B-D of the remotevehicles 104B-D. While the lead vehicle 104A is shown in FIG. 1 at oneend of the vehicle system 106, the lead vehicle 104A need not be locatedat either end of the vehicle system 106 or be located ahead of thevehicles 104B-D along a direction of travel of the vehicle system 106.

In operation, the communication devices 102 on the same vehicle system106 wirelessly communicate with each other within the timed constraintsdictated by a messaging cycle. The messaging cycle defines a schedulethat dictates when different communication devices 102 are allowed tocommunicate (e.g., send and/or receive wireless signals). The messagingcycle can prevent multiple, different communication devices 102 onboarddifferent vehicle systems 106 from wirelessly communicating messages atthe same time, which can result in messages not being received due towireless interference between the competing vehicle systems 106.

FIG. 2 illustrates one example of several vehicle systems 106 (e.g.,vehicle systems 106E-G) within wireless range of each other. The vehiclesystem 106E can represent the vehicle system 106 shown in FIG. 1, andthe vehicle systems 106F, 106G can represent additional vehicle systems106 that are separate from the vehicle system 106E but that also includecommunication systems 100 having wireless communication devices 102disposed onboard vehicles 104 in the vehicle systems 106F, 106G. Eachcommunication system 100 has a wireless range 200E-G. As shown, thewireless ranges 200E-G of different communication systems 100 overlapeach other. If these communication systems 100 use the same channel forsending wireless signals, then the wireless signals communicated betweenvehicles 104 in one vehicle system 106 can interfere with the wirelesssignals communicated between vehicles 104 in another vehicle system 106.Because these signals may include directions for changes in how thevehicles 104 in the vehicle systems 106 move (e.g., throttle settingchanges and/or brake setting changes), interference with successfulcommunication of the signals can pose a significant threat to safeoperation of the vehicle systems 106.

To prevent or reduce the likelihood of this interference, thecommunication systems 100 use the defined messaging cycles to restrictwhen different vehicle systems 106 are permitted to communicate. FIG. 3illustrates one example of a timing diagram for a messaging cycle 300 ofone of the vehicle systems 106. The timing diagram is shown alongside ahorizontal axis 302 that is representative of time. A vertical axis 304represents when the communication devices 102 onboard the differentvehicles 104 of the same vehicle system 106 communicate according to themessaging cycle 300.

The communication device 102A onboard the lead vehicle 104A is turned onor otherwise activated during an activation time slot 306 of themessaging cycle 300. During this time period 306, the radio of thecommunication device 102A may be activated from a state where the radiois not receiving power or is not actively transmitting, broadcasting, orreceiving signals. The communication device 102A sends a command messageduring a subsequent outbound time slot 308 of the messaging cycle 300.During this outbound time slot 308, the communication device 102A of thelead vehicle 104A sends a wireless command signal to the communicationdevices 102B-D of the remote vehicles 104B-D. This command signaldirects the remote vehicles 104B-D to maintain or change one or moreoperational settings of the vehicles 104B-D, such as maintaining orchanging a throttle setting, maintaining or changing a brake setting, orthe like.

The communication device 102B onboard the first remote vehicle 104Bactivates during an activation time slot 310B. The communication device102B receives the command message from the communication device 102Aonboard the lead vehicle 104A and repeats or re-sends the commandmessage as a repeated or relayed message during a subsequent relay timeslot 312B. During this time slot 312B, the communication device 102Bwirelessly sends the command message received from the communicationdevice 102A onboard the lead vehicle 104A to the communication devices102C, 102D of one or more other remote vehicles 104C, 104D. Thecommunication device 102B wirelessly sends a reply message to thecommunication device 102A of the lead vehicle 104A during a subsequentinbound time slot 314B. During this time slot 314B, the communicationdevice 102B wirelessly sends a message to the communication device 102Aof the lead vehicle 104A to indicate that the command message wasreceived by the communication device 102B of the remote vehicle 104B.

The remote vehicles 104C, 104D similarly have additional correspondingactivation time periods 310C, 310D during which the communicationdevices 102C, 102D are activated, relay time slots 312C, 312D duringwhich the communication devices 102C, 102D relay the command messageoriginally sent by the communication device 102A (and potentiallyrelayed by one or more other communication devices 102), and reply timeslots 314C, 314D during which the communication devices 102C, 102Drespond to the communication device 102A to indicate receipt of thecommand message. The messaging cycle 300 terminates after the last replytime slot 314D of the communication device 102 of the last remotevehicle 104 in the vehicle system 106.

The messages communicated within the message cycle 300 may all becommunicated by the communication devices 102 using the same channel(e.g., frequency) and the same modulation scheme (e.g., an analogmodulation scheme, such as FSK modulation) to ensure that all messagesare successfully received. The various time periods of the messagingcycle 300 are assigned to be non-overlapping time periods to preventmultiple communication devices 102 in the same vehicle system 106 fromcommunicating messages at the same time using the same channel.

The communication devices 102A onboard the lead vehicles 104A in thedifferent vehicle systems 106 may wait for a designated period of timeafter the messaging cycle 300 of one vehicle system 106 is completedbefore seizing the channel and sending another command message foranother vehicle system 106. For example, the communication device 102Aonboard the lead vehicle 104A in the vehicle system 106F may receivemessages sent by communication devices 102 onboard another vehiclesystem 106E during the messaging cycle 300 of that vehicle system 106Eon a channel being used by the communication systems 100. The leadcommunication device 102A onboard the vehicle system 106F may wait adesignated period of time after the messaging cycle 300 of the vehiclesystem 106E completes before sending any command message. This delay canprovide the communication devices 102 onboard the vehicle system 106E tocomplete successful communication of the command message, relaymessages, and reply messages. This delay can be referred to as a guardinterval.

FIG. 4 illustrates one example of a timing diagram having guardintervals 400. The timing diagram is shown alongside a horizontal axis402 that is representative of time. A vertical axis 404 represents whendifferent messaging cycles 300 of different vehicle systems 106 occur.The messaging cycle 300E represents the messaging cycle 300 of thecommunication devices 102 onboard the vehicle system 106E, the messagingcycle 300F represents the messaging cycle 300 of the communicationdevices 102 onboard the vehicle system 106F, and the messaging cycle300G represents the messaging cycle 300 of the communication devices 102onboard the vehicle system 106G. A guard interval 400 occurs afterconclusion of each messaging cycle 300. For example, a guard interval400 may begin at a time 408E after the last remote communication device102 onboard the vehicle system 106E sends the reply message to the leadcommunication device 102A of the same vehicle system 106E. Similarly, aguard interval 400 may begin at a time 408F after the last remotecommunication device 102 onboard the vehicle system 106 sends the replymessage to the lead communication device 102A of the same vehicle system106F. A guard interval 400 may begin at a time 408G after the lastremote communication device 102 onboard the vehicle system 106 sends thereply message to the lead communication device 102A of the same vehiclesystem 106G, and so on.

The command, relay, and reply messages or signals sent during themessaging cycle 300 of a vehicle system 106 can be sent on a designatedchannel using a first modulation scheme, such as an analog modulationscheme (e.g., FSK modulation). The messages or signals may includeidentifying information of the communication device 102, vehicle 104,and/or vehicle system 106 from where the message originated. Forexample, a header or preamble of the messages may include a uniqueidentifier associated with the communication device, vehicle, or vehiclesystem from which the message originated. Once the lead communicationdevice 102A of a vehicle system 106 sends a command message, thecommunication system 100 that includes that lead communication device102A seizes or maintains control of the channel for the entirety of themessaging cycle 300 for that vehicle system 106. This channelexclusivity allows for data communication between the communicationdevices 102 of that vehicle system 106 to occur exclusively on thechannel without interference from communication between othercommunication devices 102 onboard other vehicle systems 106 using thesame channel.

The communication devices 102 onboard the other vehicle systems 106F,106G also may receive the messages sent from the vehicle system 106Ehaving control of the channel during the messaging cycle 300 of thatvehicle system 106E. One or more of these communication devices 102 ofthe other vehicle systems 106F, 106G can determine that the receivedmessage was sent from a communication device 102 of the vehicle system106E based on the identifying information contained in the commandmessage. The communication devices 102 of the other vehicle systems106F, 106G may hold off on sending any messages on the channel until themessaging cycle 300 of the vehicle system 106E is complete and afterexpiration of the guard interval 400 following the messaging cycle 300of the vehicle system 106E.

Following the end of the guard interval 400, the lead communicationdevice 102A onboard another vehicle system 106 (e.g., the vehicle system106F) can begin the messaging cycle 300F of that vehicle system 106F ata starting time 408F. For example, the lead communication device 102A ofthe vehicle system 106F can activate during the activation time slot 306and can send a command message during the outbound time slot 308following the starting time 408F. The starting time 408F occurs afterthe guard interval 400 ends to prevent interference or conflict betweenmessages sent among the communication devices 102 onboard the vehiclesystem 106E and messages sent among the communication devices 102onboard the vehicle system 106F. The communication devices 102 onboardother vehicle systems 106 (e.g., the vehicle system 106G) may wait forthe guard interval 400 that begins after the messaging cycle 400F of thevehicle system 106F is complete before beginning the messaging cycle300G of the vehicle system 106G at a starting time 408G.

The communication devices 102 onboard a vehicle system 106 cancommunicate messages (also referred to as signals) with each other usingthe same channel but a different modulation scheme during the guardinterval 400. During the messaging cycle 300 of a vehicle system 106,the messages or signals are sent using a first modulation scheme, suchas an analog modulation scheme). During the guard interval 400 thatfollows the messaging cycle 300 (e.g., immediately follows or followsafter a delay), one or more remote communication devices 102 can sendstatus messages 406 (also referred to as status signals) to the leadcommunication device 102A using a second modulation scheme that isincompatible with the first modulation scheme. For example, during themessaging cycle 300E, the communication devices 102 of the vehiclesystem 106E can communicate command, relay, and/or reply signals usinganalog modulation on a channel while, during the guard interval 400 thatfollows the messaging cycle 300E, the communication devices 102 of thesame vehicle system 106E can communicate status signals using digitalmodulation on the same channel. Alternatively, during the messagingcycle 300E, the communication devices 102 of the vehicle system 106E cancommunicate command, relay, and/or reply signals using digitalmodulation on a channel while, during the guard interval 400 thatfollows the messaging cycle 300E, the communication devices 102 of thesame vehicle system 106E can communicate status signals using analogmodulation on the same channel.

The status signals may be communicated only from the communicationdevices 102 on the remote vehicles 104 to the lead vehicle 106 in thesame vehicle system 106, or alternatively may be communicated betweenany communication devices 102 in the same vehicle system 106, during theguard interval 400. For example, the second modulation scheme may onlybe used by the communication devices 102 during the guard interval 400,while the first modulation scheme is only used by the communicationdevices 102 during the messaging cycle 300 that precedes the guardinterval 400.

The status signal may be sent using the incompatible second modulationscheme due to the second modulation scheme being able to include agreater amount of data in signals than the first modulation scheme. Forexample, more data may be communicated at a faster data transmissionrate between communication devices 102 using digital modulation on asingle frequency channel than using analog modulation on the same singlefrequency channel. Use of the digital modulation scheme during the guardintervals 400 can significantly increase the amount of data that can becommunicated between the communication devices 102 during an otherwiseunused time period.

In one embodiment, the status signal includes sensor data from one ormore sensors onboard a remote vehicle 104 in the vehicle system 106.FIG. 5 illustrates one example of one of the vehicles 104 shown inFIG. 1. The communication device 102 can represent hardware circuitrythat includes and/or is connected with one or more processors (e.g., oneor more microprocessors, one or more field programmable gate arrays, oneor more controllers, and/or one or more integrated circuits) thatperform the operations described herein in connection with thecommunication device 102. The communication device 102 can includetransceiving circuitry, such as a radio, transceiver, modem, antenna120, or the like.

The vehicle 104 also includes a propulsion system 530 and a brake system532. The propulsion system 530 can include equipment that operates togenerate tractive effort to propel the vehicle 104. For example, thepropulsion system 530 can include one or more engines, alternators,generators, batteries or other energy storage devices (e.g., capacitors,flywheels, etc.), and/or motors that operate to rotate wheels of thevehicle 104. The brake system 532 can include equipment that operates togenerate braking effort to slow or stop movement of the vehicle 104. Forexample, the brake system 532 can include one or more friction brakes,regenerative brakes (e.g., motors), or the like, that slow or stoprotation of the wheels. Optionally, the brake system 532 may be part ofthe propulsion system 530. The motor(s) that propel the vehicle 104 forthe propulsion system 530 also can use regenerative braking to slow orstop movement of the vehicle 104.

A controller 536 of the vehicle 104 controls operation of the propulsionsystem 530 and/or the brake system 532 to control movement of thevehicle 104. The controller 536 represents hardware circuitry thatincludes and/or is connected with one or more processors (e.g., one ormore microprocessors, one or more field programmable gate arrays, and/orone or more integrated circuits) that perform the operations of thecontroller 536. The controller 536 can receive input from an operator ofthe vehicle 104 (e.g., manual actuation of a throttle, pedal, lever,button, touchscreen, or the like) and can change the tractive effortand/or braking effort created by the propulsion system 530 and/or brakesystem 532 to implement the operator-directed change in movement of thevehicle 104. The controller 536 optionally can receive command signalsvia the communication device 102 from the lead vehicle 104 in the samevehicle system 106 and/or from other equipment (onboard or off-board thevehicle system 106). These command signals may direct the controller 536to change operation of the vehicle 104.

Sensors 538 onboard the vehicle 104 can include cameras, radar systems,antennas, radio frequency identification tag readers, location sensors(e.g., global positioning system receivers), accelerometers, or thelike, that measure or otherwise determine characteristics related tooperation of the vehicle 104. This sensor data may include too muchinformation to be sent during the messaging cycle 300 using the firstmodulation scheme (e.g., analog modulation) on the single frequencychannel. The faster communication rates and/or greater data bandwidth ofusing the second modulation scheme (e.g., digital modulation) on thesingle frequency channel during the guard intervals 400 can allow forincreased amounts of sensor data from the sensors 538 to be communicatedbetween the vehicles 104.

The sensor data can be received by processing equipment 542 onboard thevehicle 104 from another vehicle 104. The processing equipment 542 canrepresent hardware circuitry that includes and/or is connected with oneor more processors that use the sensor data to perform one or morefunctions of the vehicle system 106. For example, the processingequipment 542 can examine the sensor data to determine that a componentonboard the vehicle system 106 has failed or is about to fail, that anobject is present on the route ahead of the vehicle system 106, thatwayside equipment has failed, or the like. Optionally, the sensor datacan be stored in a tangible and non-transitory computer-readable storagemedium 546 (e.g., “memory” in FIG. 5), such as a computer hard drive,flash drive, optical disc, or the like.

FIG. 6 illustrates a flowchart of one embodiment of a method 600 forcommunicating within a vehicle system 106 shown in FIG. 1. The method600 can represent the operations performed by one or more of thecommunication devices 102 onboard a vehicle system 106 shown in FIG. 1.At 602, one or more messages sent from remote vehicles in anothervehicle system are received. For example, the lead communication device102A onboard the vehicle system 106E can receive or detect wirelesscommunication of reply messages or signals sent by the remote vehicles104 in another vehicle system 106F, 106G that currently has control ofthe single frequency channel.

At 604, a determination is made as to whether the last remote vehicle inthe vehicle system having control over the channel has sent the replymessage to the lead vehicle of that vehicle system. For example, thelead communication device 102 of the vehicle system 106E can determinewhether the messaging cycle 300 of the vehicle system 106F havingcontrol of the channel is complete (e.g., by all remote vehicles 104 inthe vehicle system 106F having sent a reply signal to the lead vehicle104 of that vehicle system 106F). If one or more additional remotevehicles 104 in the vehicle system 106F still need to reply to thecommand message sent by the lead vehicle 104A in the vehicle system106F, then the messaging cycle 300 of the vehicle system 106F may notyet be completed. As a result, flow of the method 600 can return toward602. Otherwise, the messaging cycle 300 of the vehicle system 106F maybe complete and the channel may be available for the communicationsystem 100 of the vehicle system 106E. Flow of the method 600 canproceed from 604 toward 606.

At 606, the lead communication device waits for a guard interval to end.The lead communication device 102A of the vehicle system 106E attemptingto seize the channel for communication by the vehicle system 106E canwait for the guard interval 400 following the messaging cycle 300 of theother vehicle system 106F to end. This can allow the communicationdevices 102 of the other vehicle system 106F to communicate using theincompatible modulation scheme on the same channel used for the command,relay, and reply messages.

At 608, a lead communication device of the vehicle system seizes thechannel by sending a command message to one or more remote vehicles inthe same vehicle system. As described above, the lead communicationdevice 102A of the vehicle system 106E can take control of the singlefrequency channel by wirelessly communicating a command signal to theremote vehicles 104 of the same vehicle system 106E. This can begin themessaging cycle 300 of the vehicle system 106E. The command signal canbe communicated using a first modulation scheme, such as an analogmodulation scheme.

At 610, a reply message is received from one or more of the remotevehicles in the vehicle system having control of the channel. Forexample, the lead communication device 102A of the vehicle system 106Ehaving control of the channel receives reply signals from thecommunication device 102 onboard one or more of the remote vehicles 104in the same vehicle system 106E. The reply signals can be communicatedusing the first modulation scheme, such as an analog modulation scheme.

At 612, a determination is made as to whether the last remote vehicle inthe vehicle system having control over the channel has sent the replymessage to the lead vehicle of that vehicle system. For example, thelead communication device 102A of the vehicle system 106E can determinewhether the messaging cycle 300 of the vehicle system 106E havingcontrol of the channel is complete (e.g., by all remote vehicles 104 inthe vehicle system 106E having sufficient time to send a reply signal tothe lead vehicle 104 of that vehicle system 106E). If one or moreadditional remote vehicles 104 in the vehicle system 106E still need toreply to the command message sent by the lead vehicle 104A in thevehicle system 106E, then the messaging cycle 300 of the vehicle system106E may not yet be completed. As a result, flow of the method 600 canreturn toward 608. Otherwise, the messaging cycle 300 of the vehiclesystem 106E may be complete. Flow of the method 600 can proceed from 610toward 614.

At 614, a status message can be communicated between communicationdevices onboard the vehicle system using the second, incompatiblemodulation scheme on the same channel. For example, the communicationdevice 102 onboard one or more of the remote vehicles 104 in the vehiclesystem 106E can send status signals to the lead communication device102A of the vehicle system 106E during the guard interval 400 and usingthe second modulation scheme, as described above. Optionally, two ormore other communication devices 102 can communicate status signals orother signals using the second modulation scheme.

At 616, a determination is made as to whether the guard interval of thevehicle system has ended. If the guard interval 400 of the vehiclesystem 106E has not ended, then the communication devices 102 of thevehicle system 106E can continue communicate using the second modulationscheme to communicate signals or messages with each other. As a result,flow of the method 600 can return toward 614. But, if the guard interval400 of the vehicle system 106E has ended, then the channel may need tobe relinquished for one or more other vehicle systems 106F, 106G to use.As a result, flow of the method 600 can proceed toward 618.

At 618, the channel is relinquished to the communication system ofanother vehicle system. The channel can be relinquished by the leadcommunication device 102A of the vehicle system 106E not sending anycommand or other signals using the channel until the channel isavailable again for use by the vehicle system 106E. Flow of the method600 can then return toward 602 or may terminate.

In one embodiment, a locomotive communication system includes a leadcommunication device configured to wirelessly communicate a commandmessage to one or more remote communication devices onboard a railvehicle system during a messaging cycle. The lead communication deviceis configured to receive one or more reply messages from the one or moreremote communication devices during the messaging cycle in response tocommunicating the command message. The lead communication device also isconfigured to receive a status signal from at least one of the remotecommunication devices during a guard interval that follows completion ofthe messaging cycle. The lead communication device is configured tocommunicate the command message and receive the one or more replymessages using a first modulation comprising one of analog modulation ordigital modulation. The lead communication device also is configured toreceive the status signal using a different, second modulationcomprising the other of the analog modulation or the digital modulation.The lead communication device also is configured to communicate thecommand message and receive the one or more reply messages and thestatus signal using a designated frequency channel.

Optionally, the analog modulation is frequency shift key modulationand/or the digital modulation is phase shift key modulation. Thedesignated frequency channel may be a single frequency.

The lead communication device can be configured to send the commandmessage during the messaging cycle using frequency shift key modulationand using a communication channel that consists of a single frequency,the lead communication device also can be configured to receive thestatus signal during the guard interval using phase shift key modulationand using the communication channel that consists of the singlefrequency, and the lead communication device can be configured toreceive the one or more reply messages during the messaging cycle usingthe communication channel that consists of the single frequency.

The lead communication device can be configured to not send any signalusing the first modulation during the guard interval that follows themessaging cycle.

The lead communication device may be disposed onboard a lead locomotivein a rail vehicle system and the one or more remote communicationdevices may be disposed onboard one or more remote locomotives in therail vehicle system. The lead communication device can be configured tosend one or more of a throttle command or a brake command to the one ormore remote locomotives in the command message sent during the messagingcycle, to receive a confirmation that the one or more remote locomotivesreceived the one or more of the throttle command or the brake command inthe one or more reply messages during the messaging cycle, and toreceive sensor data from at least one of the one or more remotelocomotives in the status signal during the guard interval.

In one embodiment, a method includes wirelessly communicating a commandmessage from a lead communication device to one or more remotecommunication devices onboard a rail vehicle system during a messagingcycle, wirelessly receiving one or more reply messages from the one ormore remote communication devices during the messaging cycle in responseto communicating the command message, and wirelessly receiving a statussignal from at least one of the remote communication devices during aguard interval that follows completion of the messaging cycle. Thecommand message and the reply message are communicated using a firstmodulation comprising one of analog modulation or digital modulation.The status signal is received using a different, second modulationcomprising the other of the analog modulation or the digital modulation.The command message, the reply message, and the status signal arecommunicated using a designated frequency channel.

Optionally, the analog modulation is frequency shift key modulationand/or the digital modulation is phase shift key modulation. Thedesignated single frequency channel can be a single frequency.

The command message can be communicated during the messaging cycle usingfrequency shift key modulation and using a communication channel thatconsists of a single frequency. The status signal can be received duringthe guard interval using phase shift key modulation and using thecommunication channel that consists of the single frequency. The replymessage can be received during the messaging cycle using thecommunication channel that consists of the single frequency.

The first modulation may not be used to communicate any message duringthe guard interval that follows the messaging cycle in one embodiment.

The command message can include one or more of a throttle command or abrake command for one or more remote locomotives in the rail vehiclesystem, the reply message can include a confirmation that the one ormore remote locomotives received the one or more of the throttle commandor the brake command, and the status signal can include sensor data fromat least one of the one or more remote locomotives.

In one embodiment, a locomotive communication system includes a leadcommunication device configured to be disposed onboard a lead locomotiveof a rail vehicle system. The lead communication device is configured tocommunicate with one or more remote communication devices according to adefined messaging cycle to control movement of the rail vehicle system.The one or more remote communication devices are disposed onboard one ormore remote locomotives in the rail vehicle system. The messaging cycleincludes a first time slot for the lead communication device to send acommand signal to the one or more remote communication devices using afirst modulation scheme on a single frequency channel and one or moresubsequent second time slots for the one or more remote communicationdevices to send a reply signal to the lead communication device usingthe first modulation scheme on the single frequency channel. The leadcommunication device is configured to receive a status signal from atleast one of the remote communication devices using a second modulationscheme on the single frequency channel. The first modulation scheme andthe second modulation scheme are incompatible with each other.

Optionally, the lead communication device is configured to receive thestatus signal only during a guard interval that follows the messagingcycle and during which no other vehicle system is able to use the singlefrequency channel for communication.

The first modulation scheme can be an analog modulation scheme and thesecond modulation scheme can be a digital modulation scheme.

The status signal can include sensor data. The command signal can directa change in one or more of a throttle setting or a brake setting of theone or more remote locomotives.

In an embodiment, a system includes a lead communication deviceconfigured to be disposed onboard a vehicle system. The leadcommunication device is configured to wirelessly communicate a commandmessage to one or more remote communication devices onboard the vehiclesystem during a messaging cycle. The lead communication device isconfigured to wirelessly receive one or more reply messages from the oneor more remote communication devices during the messaging cycle inresponse to communicating the command message. The lead communicationdevice is configured to wirelessly receive a status signal from at leastone of the remote communication devices during a guard interval thatfollows completion of the messaging cycle. The command message and thereply message are communicated using a first modulation comprising oneof analog modulation or digital modulation. The status signal isreceived using a different, second modulation comprising the other ofthe analog modulation or the digital modulation. The command message,the reply message, and the status signal are communicated using adesignated frequency channel.

For example, in an embodiment of the system described in the precedingsection, the analog modulation may be frequency shift key modulation,the digital modulation may be phase shift key modulation, and/or thedesignated single frequency channel may be a single frequency. Inanother embodiment, alternatively or additionally, the leadcommunication device is configured to wirelessly communicate the commandmessage during the messaging cycle using frequency shift key modulationand using a communication channel that consists of a single frequency,to receive the status signal during the guard interval using phase shiftkey modulation and using the communication channel that consists of thesingle frequency, and to receive the reply message during the messagingcycle using the communication channel that consists of the singlefrequency. Additionally or alternatively, the first modulation is notused to communicate any message during the guard interval that followsthe messaging cycle.

In an embodiment of the system described in the preceding two sections,the command message may include one or more of a throttle command or abrake command for one or more remote vehicles in the vehicle system, thereply message may include a confirmation that the one or more remotevehicles received the one or more of the throttle command or the brakecommand, and/or the status signal may include sensor data from at leastone of the one or more remote vehicles.

As used herein, an element or step recited in the singular and proceededwith the word “a” or “an” does not exclude plural of said elements orsteps, unless such exclusion is explicitly stated. Furthermore,references to “one embodiment” of the presently described subject matterare not intended to be interpreted as excluding the existence ofadditional embodiments that also incorporate the recited features.Moreover, unless explicitly stated to the contrary, embodiments“comprising” or “having” an element or a plurality of elements having aparticular property may include additional such elements not having thatproperty.

The above description is illustrative, and not restrictive. For example,the above-described embodiments (and/or aspects thereof) may be used incombination with each other. In addition, many modifications may be madeto adapt a particular situation or material to the teachings of thesubject matter set forth herein without departing from its scope. Whilethe dimensions and types of materials described herein are intended todefine the parameters of the disclosed subject matter, they are by nomeans limiting and are exemplary embodiments. Many other embodimentswill be apparent to those of skill in the art upon reviewing the abovedescription. The scope of the subject matter described herein should,therefore, be determined with reference to the appended claims, alongwith the full scope of equivalents to which such claims are entitled. Inthe appended claims, the terms “including” and “in which” are used asthe plain-English equivalents of the respective terms “comprising” and“wherein.” Moreover, in the following claims, the terms “first,”“second,” and “third,” etc. are used merely as labels, and are notintended to impose numerical requirements on their objects. Further, thelimitations of the following claims are not written inmeans-plus-function format and are not intended to be interpreted basedon 35 U.S.C. § 112(f), unless and until such claim limitations expresslyuse the phrase “means for” followed by a statement of function void offurther structure.

This written description uses examples to disclose several embodimentsof the subject matter set forth herein, including the best mode, andalso to enable a person of ordinary skill in the art to practice theembodiments of disclosed subject matter, including making and using thedevices or systems and performing the methods. The patentable scope ofthe subject matter described herein is defined by the claims, and mayinclude other examples that occur to those of ordinary skill in the art.Such other examples are intended to be within the scope of the claims ifthey have structural elements that do not differ from the literallanguage of the claims, or if they include equivalent structuralelements with insubstantial differences from the literal languages ofthe claims.

What is claimed is:
 1. A vehicle communication system comprising: a leadcommunication device configured to wirelessly communicate a commandmessage to one or more remote communication devices onboard a vehiclesystem during a messaging cycle, the lead communication deviceconfigured to receive one or more reply messages from the one or moreremote communication devices during the messaging cycle in response tocommunicating the command message, the lead communication device alsoconfigured to receive a status signal from at least one of the remotecommunication devices during a guard interval that follows completion ofthe messaging cycle, wherein the lead communication device is configuredto communicate the command message and receive the one or more replymessages using a first modulation, wherein the lead communication deviceis configured to receive the status signal using a different, secondmodulation, wherein the lead communication device is configured tocommunicate the command message and receive the one or more replymessages and the status signal using a designated frequency channel, andwherein the lead communication device is configured to send one or moreof a throttle command or a brake command to the one or more remotevehicles in the command message sent during the messaging cycle, thelead communication device is configured to receive a confirmation thatthe one or more remote vehicles received the one or more of the throttlecommand or the brake command in the one or more reply messages duringthe messaging cycle, and the lead communication device is configured toreceive sensor data from at least one of the one or more remote vehiclesin the status signal during the guard interval.
 2. The vehiclecommunication system of claim 1, wherein the first modulation isfrequency shift key modulation.
 3. The vehicle communication system ofclaim 1, wherein the second modulation is phase shift key modulation. 4.The vehicle communication system of claim 1, wherein the designatedfrequency channel is a single frequency.
 5. The vehicle communicationsystem of claim 1, wherein the lead communication device is configuredto send the command message during the messaging cycle using frequencyshift key modulation and using a communication channel that consists ofa single frequency, the lead communication device also configured toreceive the status signal during the guard interval using phase shiftkey modulation and using the communication channel that consists of thesingle frequency, and the lead communication device is configured toreceive the one or more reply messages during the messaging cycle usingthe communication channel that consists of the single frequency.
 6. Thevehicle communication system of claim 1, wherein the lead communicationdevice is configured to not send any signal using the first modulationduring the guard interval that follows the messaging cycle.
 7. Thevehicle communication system of claim 1, wherein the lead communicationdevice is configured to be disposed onboard a lead vehicle in a vehiclesystem and the one or more remote communication devices are configuredto be disposed onboard one or more remote vehicles in the vehiclesystem.
 8. A method comprising: wirelessly communicating a commandmessage from a lead communication device to one or more remotecommunication devices onboard a vehicle system during a messaging cycle;wirelessly receiving one or more reply messages from the one or moreremote communication devices during the messaging cycle in response tocommunicating the command message; and wirelessly receiving a statussignal from at least one of the remote communication devices during aguard interval that follows completion of the messaging cycle, whereinthe command message and the reply message are communicated using a firstmodulation, wherein the status signal is received using a different,second modulation, wherein the command message, the reply message, andthe status signal are communicated using a designated frequency channel,and wherein the command message includes one or more of a throttlecommand or a brake command for one or more remote vehicles in thevehicle system, the reply message includes a confirmation that the oneor more remote vehicles received the one or more of the throttle commandor the brake command, and the status signal includes sensor data from atleast one of the one or more remote vehicles.
 9. The method of claim 8,wherein the first modulation is frequency shift key modulation.
 10. Themethod of claim 8, wherein the second modulation is phase shift keymodulation.
 11. The method of claim 8, wherein the designated singlefrequency channel is a single frequency.
 12. The method of claim 8,wherein the command message is communicated during the messaging cycleusing frequency shift key modulation and using a communication channelthat consists of a single frequency, the status signal is receivedduring the guard interval using phase shift key modulation and using thecommunication channel that consists of the single frequency, and thereply message is received during the messaging cycle using thecommunication channel that consists of the single frequency.
 13. Themethod of claim 8, wherein the first modulation is not used tocommunicate any message during the guard interval that follows themessaging cycle.
 14. A vehicle communication system comprising: a leadcommunication device configured to be disposed onboard a lead vehicle ofa vehicle system; wherein the lead communication device is configured tocommunicate with one or more remote communication devices according to adefined messaging cycle to control movement of the vehicle system, theone or more remote communication devices disposed onboard one or moreremote vehicles in the vehicle system, the messaging cycle including afirst time slot for the lead communication device to send a commandsignal to the one or more remote communication devices using a firstmodulation scheme on a single frequency channel and one or moresubsequent second time slots for the one or more remote communicationdevices to send a reply signal to the lead communication device usingthe first modulation scheme on the single frequency channel, wherein thelead communication device is configured to receive a status signal fromat least one of the remote communication devices using a secondmodulation scheme on the single frequency channel, wherein the firstmodulation scheme and the second modulation scheme are incompatible witheach other, and wherein the status signal includes sensor data.
 15. Thevehicle communication system of claim 14, wherein the lead communicationdevice is configured to receive the status signal only during a guardinterval that follows the messaging cycle and during which no othervehicle system is able to use the single frequency channel forcommunication.
 16. The vehicle communication system of claim 14, whereinthe first modulation scheme is an analog modulation scheme and thesecond modulation scheme is a digital modulation scheme.
 17. The vehiclecommunication system of claim 14, wherein the command signal directs achange in one or more of a throttle setting or a brake setting of theone or more remote vehicles.